The market for treating cyst nematodes in sugar beets, cole crops, and particularly soybeans is very large. As synthetic contact nematicide chemistry and soil fumigants face greater scrutiny, and as new nematicide, insecticide, bactericide, and fungicide chemistry pipelines shrink due to increasing regulatory thresholds, sustainable biological pesticides such as plant extracts are becoming more important alternatives, particularly those that give similar levels of control as the conventional pesticides and fumigants. Economic and environmental conditions create opportunities for biological treatments of diseases caused by plant parasitic nematodes, insects, mites, bacteria, and fungi. As a result, there is a significant demand for more environmentally-friendly solutions that makes the investment in research and development of new biologically derived nematicides worthwhile.
Currently, $1.5 billion a year is lost to soybean cyst nematode alone. Resistant soybean varieties do not last long because of the difficult crosses for hybrids with resistance. The genetic pool is diverse and breaks resistance in 2 to 3 years on average. Applications other than seed treatments in the past have been expensive. Therefore, applying contact nematicides placed in the seed furrow at planting has been the primary application method. Because of toxicity toward animals nearby, such as birds, overhead center pivots with liquid applications of toxic compounds such as Nemacur, Temik, Furadan, Dazinat and Mocap have all fallen out of favor.
Methyl bromide, a synthetic soil fumigant, poses health and environmental hazards, and is being phased out under an international ban. Since the 1960's, methyl bromide has been used by growers to effectively sterilize fields before planting to primarily control nematodes, as well as to treat disease and weeds; however, because this toxic compound is used in gas form, more than half the amount injected into soil can eventually end up in the mr. Rising into the atmosphere, it contributes to the thinning of the ozone layer. In 2005, developed countries banned methyl bromide under the Montreal Protocol, which is an international treaty signed in 1987 to protect the stratospheric ozone layer.
Under the ban, the treaty allows limited use of methyl bromide In strawberries, almonds, and other crops that lack alternatives for both effective and affordable control of nematodes, disease, and weeds. The extent of authorized use diminishes every year and will likely end soon. Finding alternatives to methyl bromide is, thus, a priority to the USDA, which provided a $5 million grant that supported research to identify alternatives since 2010. However, no single product provides the wide spectrum of control offered by methyl bromides. Growers facing the inevitable transition to alternative products are seeking viable alternatives with varying degrees of success.
Historically, “soft” nematicides, such as those derived from bacteria or fungi, have been used. They are generally weaker and can rapidly leach through the soil, lacking the residual effect to control the nematodes. The biologically derived cinnamic acid, on the other hand, offers potent initial control, short-duration residual control, and the safety of soft nematicides. As an example, the guayule plant, also known as Parthenium argentatum Gray, is currently being grown commercially in limited quantities for the extraction of latex rubber. The concentration of cinnamic acid in the resin fraction of the guayule plant has been well known due to prior commercialization attempts for rubber extraction in the 1940's and the 1980's. However, what has not been well know until this recent discovery is the effect of various compounds and the derivatives thereof harvested from the guayule plant in treating and controlling nematodes and other plant pests has not been extensively studied. Although the guayule has been known to be resistant to endoparasitic nematodes such as root knot and lesion nematode since 1948, the assumption was that cinnamic acid exudates were the reason for reduction or non-entry of these endoparasites into the root. However, in accordance with the current invention it has been found that enzymes and plant hormones in a guayule extract are also greatly involved with multiple modes of action to control or suppress plant parasitic nematodes, insects and increase plant productivity through upregulation of plant genes.